You can further affect the shape of a spline gradient. All of the these settings have gestural equivalents in the image window (make sure that Show Widgets is enabled in the Gradient Setup menu).
Vertex X Position fieldDisplays the position along the X axis of the selected vertex.
Vertex Y Position fieldDisplays the position along the Y axis of the selected vertex.
Tangent X Position fieldDisplays the position along the X axis of the selected tangent.
Tangent Y Position fieldDisplays the position along the Y axis of the selected tangent.
Amplitude Position fieldDisplays the position of the spline as a percentage of the distance between the first and last vertex.
Amplitude Start fieldDisplays the start position of the spline. Use to set the pixel length of the spline.
Amplitude End fieldDisplays the end position of the spline. Use to set the pixel length of the spline.
Reset Shape buttonResets the spline shape.